Dying ash tree

I have a young ash tree that has all of a sudden started turning yellow (the leaves on one side and near the bottom). The only change has been that I added another bag of soil and planted marigolds around the base. Am I suffocating it? I have pics but not sure I can send them to you. HELP!

Yes, covering the roots can suffocate them. But, as it an ash tree, it may be a pest called emerald ash borer. I would have a professional come to look at the tree. This is a very serious pest that needs to be dealt with as soon as possible if it has infected a tree.